DNA polymerases are enzymes that use single-stranded DNA as a template to synthesize the complementary DNA strand. In particular, DNA polymerases can add free nucleotides to the 3′ end of a newly-forming strand resulting in elongation of the new strand in a 5′-3′ direction. Some DNA polymerases can correct mistakes in newly-synthesized DNA. This process is known as error correction. These polymerases can recognize an incorrectly incorporated nucleotide and the 3′->5′ exonuclease activity of the enzyme allows the incorrect nucleotide to be excised (this activity is known as proofreading). Following base excision, the polymerase can re-insert the correct base and replication can continue. The proofreading function gives the DNA replication much higher fidelity than it would have if synthesis were the result of only a base-pairing selection step. Brutlag, D. and Kornberg, A., J. Biol. Chem., 247:241-248 (1972). DNA polymerases with 3′-5′ proofreading exonuclease activity have a substantially lower error rate when compared with a non-proofreading exonuclease-possessing polymerase. Chang, L. M. S., J. Biol. Chem., 252:1873-1880 (1977). However, sometimes, the advantage of these polymerases is offset by its relatively low processivity that reduces the yield of DNA amplification products.